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Category:Smalltalk: Difference between revisions
→Control Structures
Line 402:
^ arg2 value</lang>
Now, we can send this message to a boolean, and pass the code to be executed conditionally as a lambda block:
<lang smalltalk>(a > 0) ifYouAreTrueThenDo:[ 'positive' printCR ] ifNotThenDo:[ 'negative' printCR ]</lang>
actually, because these two return the value of the block ethyl evaluated, it can also be used for its value (in C, the ternary if expression), as in:
<lang smalltalk>( (a > 0) ifYouAreTrueThenDo:['positive'] ifNotThenDo:['negative'] ) printCR</lang>
Finally, by adding a self-returning "value" to the Object class, we can also write:
<lang smalltalk>( (a > 0) ifYouAreTrueThenDo:'positive' ifNotThenDo:'negative' ) printCR</lang>
(knowing that the if methods send <tt>"value"</tt> to the corresponding arg and return that)
In this style, all of Smalltalk's control structures, loops, enumeration, stream readers and event the exception handling constructs are built. And since every class is open, you can easily add additional convenient control functions.
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